1. Field of the Invention
The present invention relates to a novel diazodisulfone compound suitable as a photoacid generator for chemically amplified resists which are suitable for use in precision lithography utilizing various types of radiation such as far ultraviolet rays typified by a KrF excimer laser and an ArF excimer laser, and charged particles typified by electron beams, and X-rays. The present invention also relates to a radiation-sensitive resin composition suitable for use as a chemically amplified resist which comprises the novel diazodisulfone compound.
2. Description of the Background Art
In the field of microfabrication exemplified by the manufacture of an integrated circuit device, development of a lithographic process capable of reproducing microfabrication with a line-width precision of 0.5 .mu.m or less has been pursued in recent years to achieve higher integration. To ensure microfabrication in the order of 0.5 .mu.m or less, a resist which can excellently reproduce patterns with a 0.5 .mu.m or less line-width has been required. However, it is difficult to produce such a minute pattern at high precision by conventional methods using visible light (wavelength: 700-400 nm) or near ultraviolet light (wavelength: 400-300 nm). Because of this, the use of radiation with a shorter wavelength (wavelength: less than 300 nm) has been studied.
As examples of such short wavelength radiation, a bright line spectrum of a mercury lamp (wavelength: 254 nm), far ultraviolet rays typified by a KrF excimer laser (wavelength: 248 nm) and an ArF excimer laser (wavelength: 193 nm), charged particles such as electron beams, and X-rays such as synchrotron radiation can be given. Of these, lithography using an excimer laser is regarded as promising due to high output and high efficiency. Lithography using an excimer laser requires a resist which can reproduce fine patterns with a 0.5 .mu.m or less line-width at high sensitivity and high resolution.
Chemically amplified resists comprising a photoacid generator which forms an acid upon irradiation with radioactive rays (hereinafter called "exposure") have been proposed as resists applicable to far ultraviolet ray and a KrF excimer laser. The sensitivity of the chemically amplified resist is increased by the catalytic action of the acid thus formed.
As such a chemically amplified resist, Japanese Patent Application Laid-open No. 45439/1984 discloses a combination of a resin protected with a t-butyl group or a t-butoxycarbonyl group and a photoacid generator. Japanese Patent Application Laid-open No. 52845/1985 discloses a combination of a resin protected by a silyl group and a photoacid generator. In addition to these resist compositions, there are a number of reports dealing with chemically amplified resists, such as a resist which contains a resin protected by an acetal group or a ketal group and a photoacid generator (Japanese Patent Application Laid-open No. 25850/1990).
Of the above chemically amplified resists, the resist comprising an acetal group or a ketal group has attracted attention because this resist produces only a small skirt-like foot which is a problem in basic substrates such as silicon nitride and titanium nitride used for fabrication of devices in recent years (see, for example, Proc. SPIE, Vol.3049, p 314).
However, when a stringent line-width is required such as in the case of fabricating devices with sub-half micron or less, only producing a small skirt-like foot is insufficient. Development of a chemically amplified resist which is almost completely free of a skirt-like foot has been strongly desired.
In view of the above situation of the prior art, an object of the present invention is to provide a novel diazodisulfone compound that is capable of efficiently generating an acid with high sensitivity (with low exposure energy) for various types of radiation, in particular, far ultraviolet rays represented by a KrF excimer laser, ArF excimer laser, and the like, exhibits excellent storage stability, and can provide a resist with superior resolution and patterns when used as a photoacid generator for chemically amplified resists, and a radiation-sensitive resin composition which comprises the diazodisulfone compound as a photoacid generator and can be suitably used as chemically amplified resists.